Radio remote controlled door operators have become increasingly more popular for use in residences, parking areas and other locations to which controlled access is deemed essential or desirable. The typical radio remote door operator comprises, in addition to the mechanical components of the door and door mounting system, a motor which is capable of driving the door between opened and closed positions, and a motor controller which is adapted to be connected to a power supply and which is operatively associated with the motor for controlling the movements of the door in response to various signals; for example, the controller determines whether the motor drives the door in the opening direction or in the closing direction. In addition, the controller may incorporate in whole or in part certain safety features such as automatic stop and reverse functions. In addition, the typical door operator system comprises a low power, limited range radio transmitter having a pushbutton which is actuable manually to produce a coded signal, and a radio receiver/decoder for triggering operation of the controller when the coded signal is received in the proper format.
A recent development in the evolution of door operators involves the introduction of digital rather than analog or frequency/amplitude codes thereby greatly expanding the number of available codes and the security which is available to the individual door operator owners; i.e., similar to automobile door locks, the greater the number of available codes, the less likely that a transmitter other than that which is owned and preset by the door operator owner will successfully initiate a door opening function. One digital radio tranmission/receiving/decoding system is disclosed in the U.S. Pat. No. to Umpleby et al 4,141,010, "Digital Encoder for Door Operator" issued Feb. 20, 1979; another digital system is disclosed in Wilmott, U.S. Pat. No. 3,906,348.
Despite the availability of a large number of operator codes in the digital system, many owners continue to feel uncomfortable when leaving a power garage door operator in a fully operative condition while they are away from home for long periods of time or when leaving their home or place of business unattended. It is common for many owners to physically pull the power plug on their door operators to achieve a higher level of security.
The residential garage door operator has over the years become a more and more complex device. It is now known at least through the patent literature to combine multiple function processors with the digital receiver/decoder and to incorporate into an operator system such accessory devices as gas detectors and remote monitors which operate in a line carrier signal transmission mode. However, such operators, when combined with the various accessory devices, become expensive to purchase and to install, particularly as an after-market device; i.e., to retrofit an existing home or replace an older operator. Therefore, it is desirable to provide an operator system which is capable of expansion to accommodate accessory devices both from the standpoint of initial sale price and for the purpose of opening up an after-market for add-on accessory devices.